"Then follows crystallization, and this too requires skilled workmen and extreme care. The water is evaporated and the sugar crystallized in the vacuum pans, the size crystal depending upon the temperature at which the liquid is boiled. It takes a lower temperature to form a small crystal and a higher one to form a large crystal. An expert who takes the temperature of the boiling sugar regulates what we call fine-grain or coarse-grain sugar by regulating the size of the crystals. By drawing off some of the liquid and examining it on a glass slide by electric light he can tell the precise moment at which the crystals are the right size. Each size has a name by which it is known in the trade: Diamond A; Fine Granulated; Coarse Granulated; Crystal Domino; Confectioners' A and so on."
They were walking as Mr. Hennessey talked. "After the sugar has been crystallized in the pans it passes into a mixer, where it is stirred and kept from caking until it is put into the centrifugal machines, which actually spin off the crystals. These machines are lined with gauze, and as they whirl at tremendous velocity they force out through this gauze the liquid part of the sugar and leave the sugar crystals inside the machine. When these are quite dry the bottom of the receptacle opens, and the granular sugar is dropped through into a large bin."
"But I should think it would stick together," objected Van.
"That's an intelligent objection, my boy," declared Mr. Hennessey, much pleased at Van's grasp of the subject. "It would stick if it were not dried off by a degree of heat just right to keep the particles separate and not allow them to cake. After this any dust or dirt adhering to the sugar is blown off by an air blast. The product is then ready to be pressed into moulds or cut; boxed in small packages of varying weights; or put into bags or barrels."
Mr. Hennessey led the way to another floor of the refinery.
[Illustration: "I SHOULD THINK IT WOULD STICK TOGETHER.">[
Here were automatic machines upon which empty boxes traveled along until they reached a device that filled each one with the exact number of pounds to be contained in it, the package afterward passed to women who sealed it tightly and gave it the final touch before it was shipped. Other women were packing loaf or domino sugar, while down-stairs in a cooper shop men moved about constructing with great rapidity the barrels that were to carry larger quantities of sugar to the wholesale and retail stores.
"I guess by this time you've had all the sugar-making you want for one day," declared the superintendent. "I'm afraid I've given you quite a stiff lesson. You see I am so interested in it myself that I forget to have mercy on my listeners."
He smiled down at the boys.
"I'm sure we have had a fine morning with you, Mr. Hennessey, and we certainly have learned a lot," Bob said, putting out his hand. "I can't swear, though, that we could make white sugar even now."